39 research outputs found
Are Two of the Neptune Trojans Dynamically Unstable?
The Neptune Trojans are the most recently discovered population of small
bodies in the Solar System. To date, only eight have been discovered, though it
is thought likely that the total population at least rivals that of the
asteroid belt. Their origin is still the subject of some debate. Here, we
detail the results of dynamical studies of two Neptune Trojans, 2001 QR322 and
2008 LC18. We find that both objects lie very close to boundaries between
dynamically stable and unstable regions, with a significant probability that
either or both of the objects are actually unstable on timescales of a few
hundred million years. Such instability supports the idea that at least these
two Neptune Trojans are dynamically captured objects, rather than objects that
formed in situ. This that does not, however, rule out the possibility that
these two objects were captured during Neptune's proposed post-formation
migration, and have remained as Trojans ever since.Comment: 13 pages, 4 figures, 3 tables, Accepted to appear in the
peer-reviewed proceedings of the 11th annual Australian Space Science
Conferenc
Capturing Trojans and Irregular Satellites - the key required to unlock planetary migration
It is now accepted that the Solar system's youth was a dynamic and chaotic
time. The giant planets migrated significant distances to reach their current
locations, and evidence of that migration's influence on the Solar system
abounds. That migration's pace, and the distance over which it occurred, is
still heavily debated. Some models feature systems in which the giant planets
were initially in an extremely compact configuration, in which Uranus and
Neptune are chaotically scattered into the outer Solar system. Others feature
architectures that were initially more relaxed, and smoother, more sedate
migration. To determine which of these scenarios best represents the formation
of our Solar system, we must turn to the structure of the system's small body
populations, in which the scars of that migration are still clearly visible.
We present the first results of a program investigating the effect of giant
planet migration on the reservoirs of small bodies that existed at that time.
As the planets migrate, they stir these reservoirs, scattering vast numbers of
small bodies onto dynamically unstable orbits in the outer Solar system. The
great majority of those bodies are rapidly removed from the system, through
collisions and ejections, but a small number become captured as planetary
Trojans or irregular satellites. Others are driven by the migration, leading to
a significant sculpting of the asteroid belt and trans-Neptunian region.
The capture and retention efficiencies to these stable reservoirs depend on
the particular migration scenario used. Advocates of chaotic migration from an
initially compact scenario argue that smoother, more sedate migration cannot
explain the observed populations of Trojans and irregular satellites. Our
results draw a strikingly different picture, revealing that such smooth
migration is perfectly capable of reproducing the observed populations.Comment: 13 pages, accepted for publication in the peer-reviewed proceedings
of the 12th annual Australian Space Science Conferenc
2001 QR322 – an update on Neptune’s first unstable Trojan companion
The Neptune Trojans are the most recent addition to the panoply of Solar system small body populations. The orbit of the first discovered member, 2001 QR322, was investigated shortly after its discovery, based on early observations of the object, and it was found to be dynamically stable on timescales comparable to the age of the Solar system. As further observations were obtained of the object over the following years, the best-fit solution for its orbit changed. We therefore carried out a new study of 2001 QR322’s orbit in 2010, finding that it lay on the boundary between dynamically stable and unstable regions in Neptune’s Trojan cloud, and concluding that further observations were needed to determine the true stability of the object’s orbit. Here we follow up on that earlier work, and present the preliminary results of a dynamical study using an updated fit to 2001 QR322’s orbit. Despite the improved precision with which the orbit of 2001 QR322 is known, we find that the best-fit solution remains balanced on a knife-edge, lying between the same regions of stability and instability noted in our earlier work. In the future, we intend to carry out new observations that should hopefully refine the orbit to an extent that its true nature can finally be disentangled